Tuesday, 1 January 2008

Bronowski's principle of tolerance

In The principle of tolerance, Jacob Bronowski discusses a vital but neglected characteristic of science: that ‘‘all information is imperfect’’, and ‘‘our ability to work and act in the real world depends on our accepting a tolerance in our recognition and in our language’’. The nineteenth century ideal that “science should speak the perfect factual truth has turned out to be inaccessible”. But this should not be a cause for regret, because “if things had to be identical before you could recognize them, you would never recognize anything at all”. The principle of tolerance is the judgment that two instances are sufficiently similar that we can treat them as the same for present purposes. “Tolerance – is the essential safeguard, the essential degree of coarseness which makes it possible to work with abstract entities in the real world”. Too much tolerance and you are misled by random variation; too little tolerance and you lose valuable information. The most beneficial degree of tolerance must be a matter of judgment because it cannot be determined in advance. So, the best level of tolerance is known only retrospectively, by comparing the rate of progress of science when a greater or lesser degree of tolerance is assumed. The judgment of tolerance which led to the fastest scientific progress is justified as having been the best. Science therefore needs to tolerate different judgments of tolerance among scientists, allowing a multiplicity of levels of tolerance to coexist and compete. Bronowski’s principle of tolerance locates the roots of science in the domain of human creativity, in the necessity for personal judgment in science, and in the provisional and progressive nature of scientific truth: “You have to tell the truth the way you see it. And yet you have to be tolerant of the fact that neither you nor the man you are arguing with is going to get it right”.

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In The principle of tolerance, Jacob Bronowski (1908–1974) discusses a vital but neglected characteristic of science: that ‘‘all information is imperfect’’, and ‘‘our ability to work and act in the real world depends on our accepting a tolerance in our recognition and in our language’’ [1].

The nineteenth century ideal that “science should speak the perfect factual truth has turned out to be inaccessible”. But this should not be a cause for regret, because “if things had to be identical before you could recognize them, you would never recognize anything at all”; and “if we were given the superhuman power to identify things only when they are identical, it would be fatal for us”. Indeed, the scientist “…would not be able to do any experiment at all. [He] would keep on saying to a colleague, “You are not doing it right. It is not the same experiment”.

Bronowski’s point is that two experiments are never exactly the same – and if we insisted on exactness nothing could ever be replicated. The principle of tolerance is the judgment that two instances are sufficiently similar that we can treat them as the same for present purposes. “…Tolerance – is the essential safeguard, the essential degree of coarseness which makes it possible to work with abstract entities in the real world”.

I recognize this phenomenon from my first days as an active scientist, training for the doctorate. I was learning how to perform radio-immunoassays (RIAs) to measure peptides – which was a standard methodology. My initial reaction was shock at how imprecise, how subjective, was this supposedly ‘standard’ method. There were many personal judgments required to generate each measurement, and each judgment involved a trade-off.

The usual practice was to measure each plasma sample in duplicate and average the result. I felt this was not sufficiently precise, but the more replicates used the more plasma was used; which in turn meant fewer blood tests were possible for each experimental subject – or else each subject would need to give a bigger blood sample, reducing the pool of subjects.

Counting the radioactivity of each plasma sample took a long time, and the lower was the concentration of peptide, the lower was the level of radioactivity and the larger the stochastic variation of decay; but the longer the counting procedure, the fewer experiments could be done. Defining the sensitivity limit of the assay was another judgment call. If I set the sensitivity too low I would just be measuring random noise, but if I set the threshold too high I would be missing data on differing levels of peptides.

And this is the problem in microcosm. Too much tolerance and science becomes un-reliable [2] because you are misled by random variation; too little tolerance and you lose valuable information. The too-credulous scientist may be spinning a story based on foundations of sand; but the ultra-sceptic will block progress by knocking-down every potential advance. And different scientists will make different judgments concerning the optimal level of tolerance. As so often, it is clear that a variety of personality types are necessary in the social process of science [3] and [4].

Naïve observers of science tend to regard science as characterized by the elimination of judgment and the attainment of absolute precision, but Bronowski points out that: “[The scientific process] depends on an understanding that the best scientific result in the world is not right, that the best experiment in the world is surrounded by an area of tolerance [1]”.

The key point is that the optimal degree of tolerance must be a matter of judgment because it cannot be determined in advance. The best level of tolerance is known only retrospectively, in practice, by comparing the rate of progress of science when a greater or lesser degree of tolerance is assumed. Levels of tolerance therefore compete. The judgments of tolerance which (further down the line) lead to the fastest scientific progress are justified after the fact as having been the best judgments [4]. This also suggests that science needs to be tolerant of different degrees of tolerance among scientists themselves [3], and allow a multiplicity of levels of tolerance to coexist and compete.

There are thus two pressures in science. One is to strive for ever-lower levels of tolerance and to seek ever-greater levels of precision in measurement. The other is to accept a reasonable, attainable level of tolerance so that work can proceed now.

Too much tolerance and science will be measuring random noise, too little tolerance and the progress of science will be stalled. On the one hand, science tries to be correct and accurate; on the other hand, all science is wrong, in an ultimate sense, because it will be superseded – and the proper question is whether current scientific practice is accurate enough. We need to compromise over tolerance in order to act.

Over the long term science tends to progress by becoming more precise, by including more data, and with a diminishing area of tolerance. For example, an improved technology may increase the precision of a measurement; that – indeed – was the purpose of my doctorate, to deploy a new and better immunoradiometric assay (IRMA) for the hormone ACTH. Such new and more precise measurements may contradict predictions, meaning that existing theories are challenged. A new, more complex and more-inclusive theory may be devised.

This long term trend towards lower tolerance tends to award greater short-term status to those sceptics of science who are biased in the direction of reducing tolerance, discarding data, rejecting theories. Scientists who fear being wrong will tend to err in the direction of being in-tolerant. The tendency is to generate a supply of professional nay-sayers and negativists among the community of scientists.

Another way to avoid personal criticism for mistaken judgments is to remove decisions out of the realm of judgment and submit them to convention. Whenever an interpretational decision is removed from judgment to convention it is also removed from science, and ceases to be a part of scientific communications. This tendency to standardize and routinize is an intrinsic aspect of the evolution of complex systems [5]. Once they are standardized, procedures need to be learned but do not need to be thought-about or justified: this liberates time, resources and effort to devote to developing the cutting-edge of new science. In other words, conventions of tolerance are not science but should be the result of science, and may increase the efficiency of science.

[Science] “is a process in which truth and falsity (as well as other principles, values, goods or evils) are there not in the observation itself but in the record of it which you pass to others [1]”.

In the end, therefore, subjective evaluations of tolerance are those which are intrinsic to scientific communications, and even the decision to adhere to conventional practice is itself a judgment.

However, balancing the short-term tendency to accord status to low-tolerance, nay-saying ultra-sceptics; is a longer-term tendency of science to award the greatest prestige to those yea-sayers who open up new growth areas of revolutionary science. Because, if tolerance becomes too low, this will tend to kill-off a science. When practice becomes too difficult and new information too rare, that branch of science will dry-up through lack of anything to communicate.

So in the long-term the yea-sayers ultimately overcome the nay sayers of science, from the intrinsic tendency of complex systems to perpetuate themselves [5]. Tolerance levels tend to relax sufficiently to enable scientific communication to be generated and sustained, and to grow.

Bronowski’s principle of tolerance locates the roots of science in the domain of human creativity, in the necessity for personal judgment in science, and in the provisional and progressive nature of scientific truth:

“…You have to tell the truth the way you see it. And yet you have to be tolerant of the fact that neither you nor the man you are arguing with is going to get it right [1].”